I've seen all 3 players & seen them all play 100+ games. It's very hard to compare forwards to mid fielders & even harder to compare players from different eras. To help (myself) I'll compare apples to apples first.
Dusty Vs Raines is up first. The short answer is that Dusty wins hands down! Raines was a fine player who's dash out of the middle with a booming long kick was a joy to watch ... but that's where the comparison finishes. Dusty blows Raines right off the map! Raines also made the unforgivable mistake of leaving to play for Collingwood! Game, set & match right there!
Royce was my childhood hero & I could go on & on about how great he was. Trying to stick to the facts, I still think Royce as a forward was the greatest overhead mark I have ever seen play the game (& I've watched Hudson, Jezza, Wade & McKenna & Blight at their peak). His judgement of the ball in flight was incredible, he won so many contest by simply judging where the ball was going to land & getting under it. His hands were the best I've seen - one vice-like grip on the ball was all it took. Even in the wettest weather he would often clunk the most impossible marks.
So for me its still Royce, with Dusty coming a close second.
Craig Lambert deserves a mention too, and the unforgettable Mark Eustice ... who I have ... umm ... completely forgotten about since watching Dusty ...